1. Field of the Invention
This invention relates to an apparatus in which liquid or pasty coating medium is applied directly or indirectly onto a traveling material web, especially of paper or cardboard.
2. Description of the Related Art
The application of liquid or pasty coating medium by use of a paint curtain or paint veil, the so-called "curtain coating" itself, is already known. U.S. Pat. No. 5,624,715, for example, shows a paint curtain applicator mechanism for the direct coating of a material web. To put it more precisely, U.S. Pat. No. 5,624,715 deals with the impairment/disturbance problem of the coating medium-veil's even distribution onto the material web caused by the carried-on air of the traveling material web. Furthermore, from the German patent document no. EP 0 517 223 B1, an apparatus is known with the help of which air bubbles are to be removed from the coating medium in the run-up of the application process so that the bubbles cannot influence the regularity/evenness of the application.
A further problem, which arises during "curtain coating," and with which the above mentioned printing does not deal, is the dosage of the coating medium. Usually, the coating medium applied by use of curtain coating is not metered out by a subsequent doctor device, so high demands are made on the measured emission/discharge of the coating medium from the paint curtain applicator mechanism.